CN109203988B

CN109203988B - Method for correcting the drag torque curve of at least one rotatably mounted mechanical element

Info

Publication number: CN109203988B
Application number: CN201810708410.XA
Authority: CN
Inventors: 马库斯·科尔伯克
Original assignee: Magna Powertrain GmbH and Co KG
Current assignee: Magna Powertrain GmbH and Co KG
Priority date: 2017-06-30
Filing date: 2018-07-02
Publication date: 2022-07-19
Anticipated expiration: 2038-07-02
Also published as: DE102017211227A1; US10744995B2; KR102110238B1; DE102017211227B4; US20190001951A1; KR20190003392A; CN109203988A

Abstract

The invention relates to a method for correcting the drag torque curve of at least one rotatably mounted mechanical element. In particular, a method for correcting a drag torque curve of at least one rotatable machine element, the drag torque of which depends on the rotational speed of the machine element, is provided, wherein the drag torque curve has a plurality of rotational speed ranges which differ from one another, wherein the drag torque curve in each rotational speed range is corrected between a measured rotational speed of the machine element and a calculated rotational speed of the machine element on the basis of a rotational speed deviation in the respective rotational speed range.

Description

Method for correcting the drag torque curve of at least one rotatably mounted mechanical element

Technical Field

The invention relates to a method for correcting a drag torque curve of at least one rotatably mounted mechanical element, such as, for example, a torque transmission part of a vehicle drive train, by means of which torque can be optionally transmitted to a secondary axle, for example a rear wheel axle, for the purpose of all-wheel drive.

Background

A drive train with on/off all-wheel drive may for example comprise a power transmission unit by means of which the drive torque can be distributed between a plurality of wheel axles of the vehicle as required. For this purpose, in the case of a power transmission unit described, for example, in DE 102008032477 a1, for this purpose a coupling unit is used, also referred to as an all-wheel clutch, by means of which a variable proportion of the torque can be transmitted from the input shaft of the vehicle to the auxiliary wheel shaft as required. In the case of a so-called "torque-on-demand" power transmission unit, the wheels of the primary axle are permanently driven, while a variable proportion of the driving torque can be transmitted to the wheels of the secondary axle as required by means of the mentioned coupling unit. In this case, the torque transmission to the secondary axle takes place on a torque transmitting part of the drive train, which may be, for example, a cardan shaft, which comprises a wheel axle drive which is connected to the torque transmitting part in terms of drive together with a differential of the secondary wheel axle.

Since the torque transfer part in question also rotates in the case of an all-wheel drive disconnection as a result of its towed operation by the secondary axle, in order to reduce undesirable friction losses in the case of an all-wheel drive disconnection, the torque transfer part can be closed by a closing device, as described for example in documents DE 102009005378B 4 and WO 2014/166819 a 2. This shutdown function is sometimes also referred to as "disconnect". In order to achieve the disconnection function in question, a separating or disconnecting clutch is provided in particular, which in the closed state establishes a drive-effective connection between the torque transmission part and the secondary axle and in the open state interrupts the drive connection between the torque transmission part and the secondary axle. Thus, if the disconnect clutch is opened with all-wheel drive disconnected or in a two-wheel drive mode, this has the following effect: the torque transfer part in question is decoupled from the drive train and in particular from the secondary axle and rotates freely until its rotation is stopped by the drag torque present. In this case, the drag torque of the torque transfer part depends in particular on the rotational speed of the torque transfer part, since, for example, the load friction of the torque transfer part tends to increase with increasing rotational speed.

If, once the all-wheel drive has been switched off and the torque transfer part has been switched off, the secondary axle will be switched on again for all-wheel drive purposes, the off-type clutch must on the one hand be engaged again and the all-wheel clutch must on the other hand be engaged again in order to establish a drivingly effective connection between the torque transfer part and the secondary axle. However, before the disconnect clutch can be engaged, the torque transmitting portion must be set to rotate again by means of the all-wheel clutch and in synchronism with the rotation of the secondary axle. In so doing, the torque transfer part should be accelerated uniformly, and preferably at a constant acceleration, in order to be able to predict as accurately as possible the time at which the disconnect clutch will be engaged. Therefore, it is necessary to know precisely the speed-dependent profile of the drag curve of the torque transfer part in order to be able to engage the all-wheel clutch on the basis of the speed-dependent profile of the drag torque of the torque transfer part, in order to accelerate the torque transfer part as uniformly as possible and in order to be able to predict as precisely as possible the time at which the disconnect clutch is closed.

In fact, the drag torque curve can be determined ahead of time on the test rig; however, since the drag torque profile is affected by various variables, such as, for example, varying load friction, other product-related tolerances, temperature effects, or, for example, friction effects, it would be desirable to be able to update and correct the drag torque profile of the torque transmitting portion of the vehicle driveline while driving the vehicle.

The invention is therefore based on the object of meeting this requirement.

Disclosure of Invention

This object is achieved by the method according to the invention for correcting a drag torque curve of at least one rotatably mounted mechanical element, and in particular by correcting the drag torque curve in the respective rotational speed range between a measured rotational speed of the mechanical element and a calculated rotational speed of the mechanical element on the basis of a rotational speed deviation in each rotational speed range.

Therefore, there is no overall correction of the drag torque curve, as there is no case: this is the case, for example, when the measured drag torque is compared with the calculated drag torque at any rotational speed and the entire drag torque curve is corrected based on the comparison; instead, the invention is based on the following idea: the drag torque curve is theoretically divided into a plurality of speed ranges, such as a low rotation speed range, a middle rotation speed range, and a high rotation speed range, and correction of the drag torque curve substantially independently of correction of the other rotation speed ranges is performed in each of these rotation speed ranges. In this way, the following facts can be considered: the drag torque curve may behave quite differently in different rotational speed ranges, which may be caused, for example, by the speed-dependent load friction having a quite different effect on the drag torque curve in the individual rotational speed ranges. Thus, it is contemplated according to the invention that the drag torque curve in each rotational speed range is corrected on the basis of a rotational speed deviation, which is obtained in the respective rotational speed range between the measured rotational speed and the calculated rotational speed of the mechanical element.

The determination of the rotational speed deviation and thus the correction of the drag torque curve can be carried out in the following cases: when the torque transmitting portion is not coupled, and in particular each time when the torque transmitting portion is not coupled, in particular when the torque transmitting portion is decoupled from the drive means by means of the first clutch and decoupled from the output means by means of the second clutch, or when the disconnect clutch is also disengaged after or during disconnection of the all-wheel drive by disengaging the all-wheel clutch. After the disconnection clutch is disengaged, the torque transmitting portion idles in this case until rotation of the torque transmitting portion stops. In so doing, after the disconnect clutch is opened, the rotational energy of the torque transmitting portion is consumed by the drag torque of the torque transmitting portion due to friction until the rotational speed of the torque transmitting portion is zero. During this coasting phase of the torque transmission part after the opening of the disconnect clutch, the rotational speeds in the respective rotational speed ranges are calculated on the one hand and measured on the other hand while running through the respective rotational speed range, so that a rotational speed deviation in the respective rotational speed range can be determined on the basis of a difference resulting from the measured rotational speed of the torque transmission part and the respective calculated rotational speed, in order to be able to subsequently correct a previous drag torque curve on the basis of these rotational speed deviations for a further engagement operation of the all-wheel clutch or the disconnect clutch.

Preferred embodiments of the present invention will now be discussed below. Other embodiments may arise from other further defined versions of the invention, the description of the drawings, and the drawings themselves.

Thus, according to one embodiment, it is provided that the drag torque curve in each rotational speed range is corrected by determining a correction factor assigned to the respective rotational speed range on the basis of the rotational speed deviation of the respective rotational speed range, on the basis of which correction factor the drag torque curve in the respective rotational speed range is corrected, in particular multiplied. For example, a specific correction increment for the correction of the correction factor may be assigned to each rotational speed deviation on the basis of a look-up table. As an alternative to the above-described allocation, such allocation can also be carried out by means of a function which allocates a specific correction increment to each rotational speed deviation.

According to a simple embodiment, for example, a linear correlation between the rotational speed deviation and the correction increment can be stored, wherein the correction increment increases with increasing speed as a result of the linear correlation. During the current loop iteration, the correction increment is in this case added to the correction factor from the previous loop iteration in order to obtain the correction factor for the current loop iteration in this way. Depending on whether the determined rotational speed deviation between the measured rotational speed and the calculated rotational speed is positive or negative, this will result in a positive or negative correction increment, which is added to the correction factor of the previous iteration of the loop. Thus, if the current correction factor is applied to the torque drag curve in the corresponding speed range in the current iteration of the loop, this has the following effect: the drag torque curve in the respective speed range is increased or decreased depending on the arithmetic sign of the correction increment.

According to a further embodiment, the rotational speed deviation of the respective rotational speed range may be determined by summing the rotational speed differences determined between the measured rotational speed of the mechanical element and the calculated rotational speed of the mechanical element at different times within the respective rotational speed range. The rotational speed deviation is therefore the cumulative error obtained in the respective rotational speed range, so that the individual measurement errors in the respective rotational speed range have only a minor effect on the correction of the drag torque curve.

According to another embodiment, in each rotation speed range, the rotation speed that has been initially measured is used as an initial value for calculating the rotation speed. Thus, if the individual rotational speed ranges pass one after the other during the coasting of the mechanical element, the model rotational speed or the calculated rotational speed is initially set equal to the initially measured rotational speed in the respective rotational speed range in each rotational speed range. In this way, the calculation model is adapted to the actual prevailing drag torque state, whereby it can calculate the rotational speed from this time on the basis of the initially measured rotational speed in the respective rotational speed range.

Since the rotational speed deviations in the individual rotational speed ranges can have different magnitudes in order to avoid discontinuities in the corrected drag torque curve, it can be provided according to a further embodiment that, in a predetermined rotational speed band relating to a limiting rotational speed separating or delimiting the first rotational speed range from the adjacent second rotational speed range, the drag torque curve is corrected on the basis of two correction factors assigned to the two adjacent rotational speed ranges. In other words, a speed range is defined between two adjacent speed ranges, wherein the correction factor of one speed range has an effect on the correction of the other speed range and the correction factor of the other speed range also has an effect on the correction factor of the one speed range.

For example, in a predetermined speed range associated with the limit speed, the drag torque curve can be corrected between two adjacent speed ranges in the following manner: in the first rotation speed range, the correction factor assigned to the first rotation speed range is gradually decreased and the correction factor assigned to the second rotation speed range is gradually increased as the rotation speed gradually approaches the limit rotation speed. In the second rotational speed range, the correction factor assigned to the first rotational speed range is further gradually reduced, preferably up to zero, as the rotational speed becomes gradually farther from the limit rotational speed, and likewise the correction factor assigned to the second rotational speed range is further gradually increased. Thus, if, for example, an intermediate speed range is taken into account, the correction factor for this intermediate speed range is always smaller as the speed approaches the limit speed associated with the next higher speed range, in which the correction factor for the next higher speed range becomes progressively larger as the speed approaches the limit speed associated with the next higher speed range. In other words, the closer the rotational speed is to the limit rotational speed associated with the adjacent rotational speed range, the less the rotational speed deviation of the rotational speed range under consideration will therefore have an effect on the correction of the drag torque curve; conversely, the closer the rotational speed is to the limit rotational speed, the greater the influence of the rotational speed deviation of the adjacent rotational speed ranges on the correction of the rotational speed range under consideration. In this way, it is possible to prevent discontinuities of the corrected drag torque curve from occurring at the limit rotational speed between two adjacent rotational speed ranges, since the correction factors of the adjacent rotational speed ranges are adapted to one another to a certain extent.

According to a further embodiment, the reduction or increase of the correction factors of adjacent rotational speed ranges in a predetermined rotational speed range in relation to the limit rotational speed between two adjacent rotational speed ranges is based on a so-called initial function, i.e. by: each speed range is assigned an initial function which is dependent on the speed and to which the correction factors of the respective speed range are multiplied. In this case, each initial function may have a maximum function value, for example one, in its assigned rotational speed range, which decreases continuously in the adjacent rotational speed range from the maximum function value in the direction of the adjacent rotational speed range to a function value of zero. The initial function may thus be, for example, a bell-shaped curve function, the function value of which decreases in both directions from a maximum value to zero, the function value reaching its respective adjacent rotational speed range in both directions. Likewise, the initial function may be, for example, a trapezoidal function with a straight descending side. The initial function should in this case be selected such that the sum of the function values of the initial functions of adjacent rotational speed ranges has a value of one at each rotational speed, so that no overcorrection or undercorrection of the drag torque curve occurs in the respective rotational speed range in relation to the limit rotational speed between the two adjacent rotational speed ranges.

As already mentioned above, the correction factor is updated after each loop iteration by means of a correction increment for the current loop iteration. For this purpose, the rotational speed deviation of the respective rotational speed range can be determined by summing the rotational speed differences determined between the measured rotational speeds of the mechanical element at different times in the respective rotational speed range and the rotational speed of the mechanical element calculated taking into account the corrected drag torque curve. The updating by means of the correction increment is therefore based on the corrected drag torque curve in the previous iteration of the cycle, i.e. this is used in the previous rotational speed range for calculating the rotational speed. The correction factor updated by means of the corresponding correction increment may then be applied to the starting torque drag curve; as an alternative to this, the corresponding correction increment can be used as a correction factor and the correction factor can be applied to the corrected drag torque curve.

For completeness, it should be noted at this point that although the method according to the invention for correcting the drag torque curve of the torque transmitting part of a vehicle drive train has been explained, the method can be used in a corresponding manner for correcting the drag torque curve of any desired mechanical element. It is essential for this purpose that the respective mechanical element is set into rotation and then remains rotating itself, so that it can freewheel freely until it stops. During this coasting phase, the respective associated rotational speed deviation is determined in a plurality of mutually different rotational ranges in the manner explained above, and the drag torque curve of the mechanical element can then be corrected within the respective rotational speed range on the basis of this deviation.

The invention also relates to a method for controlling a first clutch and a second clutch of a vehicle drive train, wherein a torque transmission part of the drive train can be closed, that is to say can be decoupled from the drive train, by opening the first clutch and opening the second clutch, and wherein the torque transmission part can be coupled into the drive train, in particular in order to transmit torque to a secondary axle of the vehicle, by closing the first clutch and subsequently closing the second clutch, wherein in the control method the closing of the first clutch and/or the closing of the second clutch is/are carried out depending on a corrected or corrected torque drag curve as explained above.

Drawings

The invention will now be explained, by way of example only, with reference to the accompanying drawings, in which:

fig. 1 shows a schematic view of a drive train of a vehicle with switched-off all-wheel drive, wherein the rear wheel axle or the secondary wheel axle can be switched on and off;

FIG. 2 illustrates a reduction in rotational speed of the torque transmitting portion over time after the torque transmitting portion is decoupled, and also illustrates the determination of a rotational speed deviation in individual rotational speed ranges;

Fig. 3 shows, on the one hand, a given drag torque curve as a function of the rotational speed and, on the other hand, the initial functions assigned to the three rotational speed ranges;

FIG. 4 shows a schematic of a function for determining a correction increment; and

fig. 5 shows the correction factors corrected by means of the initial function and also the influence of these correction factors on the drag torque curve.

Detailed Description

Fig. 1 shows a drive train of a motor vehicle, in the front region of which a drive unit 12 is arranged, which drive unit 12 in the case of the embodiment shown is an internal combustion engine oriented transversely to the longitudinal axis of the vehicle. The drive unit is permanently connected to the front axle 16 of the vehicle, including the front axle differential 22, by means of the change speed gearbox 14, so that the front wheels 18, which are drivingly effectively connected to the front axle 16, can be permanently driven by the drive unit 12 during driving of the vehicle. Thus, the front axle 16 forms the primary axle 20.

In the rear region of the motor vehicle, the vehicle has a rear axle 24 with a rear axle differential 26 and rear wheels 28. The rear wheel axle 24 forms a secondary wheel axle 30, since the rear wheel axle 24 is driven by the drive unit 12 in all-wheel operation. For this purpose, a torque-controllable branching device 32 is arranged on the primary wheel axle 20, via which torque-controllable branching device 32 an adjustable proportion of the drive torque provided by the drive unit 12 can be branched off to the secondary wheel axle 30. For this purpose, the torque splitting means 32 comprise an all-wheel clutch 33, which all-wheel clutch 33 is designed as a multiplate clutch and is controlled by a control unit 34.

The output device of the multiplate clutch 33 is connected to one end of a torque transmitting portion 36, the torque transmitting portion 36 including, inter alia, a cardan shaft. The torque transfer portion 36 is connected at its other end to a bevel gear 38, the bevel gear 38 meshing with a ring gear 40, the ring gear 40 being connected to a differential housing 42 of the rear axle differential 26.

In order to prevent unnecessary and existent rotation of the torque transmission part 36, including the differential housing 42, and to dissipate energy when the multiplate clutch 33 is open, i.e. when driving with only front wheel drive, means are provided for closing the torque transmission part 36. In the case of this exemplary embodiment, the closing means are formed by a dog clutch 46, which dog clutch 46 is arranged on the half shafts 44 of the rear axle 24 in the vicinity of the rear axle differential 26, and which can likewise be controlled by the control unit 34.

In the event that the torque transfer portion 36 has been closed by means of the dog clutch 46 for driving by front wheel drive only, the torque transfer portion 36 must first be synchronized with the secondary axle 30 before the dog clutch 46 can be engaged again for torque transfer by all wheel drive. For this purpose, the multiplate clutch 33 is engaged in a controlled manner in order in this way to increase the speed of the torque transmitting part 36 again. The acceleration of the torque transmission part 36 should be carried out as uniformly as possible here, in order to be able to determine precisely in advance, on the one hand, when the dog clutch 46 can be engaged and in order, on the other hand, not to adversely affect the driving comfort, as would otherwise be the case with an uneven acceleration of the torque transmission part. Therefore, in order to be able to increase the speed of the torque transfer portion 36 as uniformly as possible, it is necessary to know the drag torque of the torque transfer portion 36, which depends on the rotational speed of the torque transfer portion 36, as can be seen by the solid line in fig. 3, with the greatest possible accuracy.

The drag torque curve m (n) represented in fig. 3 may be, for example, a drag torque curve predetermined or determined on a vehicle test stand, however, the drag torque curve may be due to friction and wearChanges over time. In order to be able to register a change in the drag torque curve and to correct the drag torque curve accordingly, the entire rotational speed range over which the torque transmission part 36 can be operated is divided into a plurality of rotational speed ranges X which differ from one another according to the invention_i. In the case of the exemplary embodiment represented here, the entire rotational speed range is divided into three rotational speed ranges, specifically a rotational speed range of low rotational speeds from 0rpm to 2000rpm, a medium rotational speed range from 2000rpm to 5000rpm and a speed range of high rotational speeds exceeding 5000 rpm. In FIG. 3, these speed ranges are represented by X₁、X₂、X₃To indicate. The drag torque curve m (n) is divided into a plurality of speed ranges in order to be able to correct the drag torque curve in a stepwise manner or in each speed range X of the drag torque curve itself_iThe drag torque curve is internally corrected. For this purpose, in each rotational speed range X_iA corresponding rotational speed range X is determined, obtained between the measured rotational speed and the calculated rotational speed of the torque transfer portion 36 _iInner rotational speed deviation N_iSo that the drag torque curve M (n) can be based on the corresponding speed range X_iThe rotational speed deviation N_iAnd is corrected.

Therefore, to calculate these rotational speed deviations N_iAfter uncoupling of the torque transfer part 36, i.e. after release of the two

clutches

33 and 46, the coasting of the torque transfer part 36 is monitored, as can be seen in the upper representation of the diagram in fig. 2, which shows the measured rotational speed n_MeasuringIs measured over time. As can be seen from the representation, after the torque transfer portion 36 is decoupled from the rest of the drive train, the rotational speed of the torque transfer portion 36 is continuously reduced until a value of zero is reached. In so doing, the torque transfer portion 36 operates through the three speed ranges X over time₃、X₂、X₁The three rotational speed ranges X₃、X₂、X₁Are separated from each other at limit speeds of 5000rpm and 2000 rpm. In these rotational speed ranges X_iIn each rotational speed range of (1), measuring the rotational speed n_MeasuringAnd calculating the rotational speed n_{Model (model)}The rotational speed deviation between them is thus calculated for correction of the drag torque curve. For this purpose, in each rotational speed range X_iAt the beginning of (2), the rotational speed n is calculated _{Model (model)}Is set equal to the measured speed n_MeasuringFrom the middle rotational speed range X, as can be seen from the upper representation in the diagram of FIG. 2₂It is seen that in this intermediate rotational speed range X₂When entering the intermediate rotation speed range, the rotation speed n is calculated_{Model (model)}And measuring the speed of rotation n_MeasuringEqual, both equal to 5000rpm, so that the rotation speed can be calculated starting from this initial value, in particular while taking into account the drag torque curve m (n).

Thus, each rotation speed range X_iRotational speed deviation N_iBy setting the speed in the corresponding speed range X_iMeasuring the speed of rotation n at different times internally_MeasuringAnd calculating the rotational speed n_{Model (model)}The obtained rotational speed difference therebetween is calculated by summing up, as represented by the middle representation of the graph in fig. 2. In the corresponding speed range X_iThe rotational speed deviation N determined here_iThe larger the actual profile of the drag torque curve is, the greater the corresponding speed range X_iThe greater the deviation of the predetermined profile in (a); therefore, in the corresponding rotational speed range X_iTorque deviation N in (1)_iThe larger the rotation speed range X, the greater the correction must be_iThe more predetermined drag torque curve m (N) there is, the drag torque curve is based on the rotational speed deviation N_iWhether positive or negative must be increased or decreased.

If it has been determined in the manner described above for each speed range X_iAssociated rotational speed deviation N_iThen correcting the factor K_xMay then depend on the speed range X for the respective rotation_iCorresponding rotational speed deviation N_iBut is determined according to the following equation:

K_x(t+1)＝K_x(t)+k_x， (1)

wherein, K_x(t) is a correction from a previous iteration of the loop for correction of the drag torque curveBy a positive factor, the value has been initialized to one. Component k_xRepresents a correction increment added to the correction factor from the previous iteration of the loop in order to obtain the correction factor K for the current correction of the drag torque curve m (n)_x(t + 1). In this case, the correction increment k_xIndicating the determined rotational speed deviation N_iHow strongly the correction of the drag torque curve m (n) is affected. Thus, the correction increment k_xIs the deviation of the rotational speed N_iAs a function of (c).

For example, fig. 4 shows a schematic representation of a method for determining the rotational speed deviation N_iTo determine a correction increment k_xAs can be seen from fig. 4, the correction increment k_xExpressed as a deviation from the rotational speed N_iApproximately proportionally. It can also be seen from fig. 4 that the negative rotational speed deviation N_iResulting in a positive correction factor k _xAnd a positive rotational speed deviation N_iResulting in a negative correction factor k_xSo as to be able to follow the rotational speed deviation N_iTo increase or decrease the drag torque curve.

Knowing the speed range X determined in this manner for each of the speed ranges_iCorrection increment k of_xFor the respective torque ranges X, can be determined based on equation (1)_iCorrection factor K of_xSo that subsequently each speed range X can be brought_iBy the associated correction factor K_xFor calibration purposes.

However, in order to avoid a discontinuity in the profile of the corrected drag torque curve in doing so, in a predetermined rotational speed band associated with a limit rotational speed separating the first rotational speed range from the adjacent second rotational speed range, for example in the rotational speed band associated with the low rotational speed range X₁With a medium speed range X₂In a separate speed band associated with a limit speed of 2000rpm, the drag torque curve M (n) may be based on the drag torque curve assigned to the two adjacent speed ranges X₁And X₂Two correction factors K_xAnd is corrected. For this purpose, for example, in a first rotational speed range X₁In (1), as the rotation speed gradually approachesA limit rotation speed of 2000rpm, assigned to the first rotation speed range X₁Correction factor K of _x1Gradually decreases and is assigned to a second rotational speed range X₂Correction factor K of_x2And gradually increases. Likewise, in the second rotational speed range X₂Is allocated to the first rotation speed range X as the rotation speed becomes gradually distant from the limit rotation speed of 2000rpm₁Correction factor K of_x1Further gradually decreases until it reaches zero, and is assigned to a second speed range X₂Correction factor K of_x2And further gradually increases.

According to the invention, the correction factor K_xIs performed here by means of a so-called initial function, which is represented in fig. 3 by a dashed and dotted curve. Each initial function A_XiIn this case, the maximum function value is dependent on the rotational speed and is equal to one, wherein in the respective adjacent rotational speed range X_iWithin, each initial function A_XiSteadily decreasing from a maximum function value equal to one to zero. Initial function A_XiIn this case, the adjacent rotational speed ranges X_iInitial function A of_XiThe sum of the function values of (a) has a value of one at each speed n.

In order to be able to adapt individual torque ranges X in a speed range associated with a respective speed limit_iCorrection factor K of_xMaking a correction to make the initial function A_XiMultiplied by the corresponding associated correction factor K _XiWith the following results: correction factor K for the respective speed range_XiIt also has an effect on the correction of the drag torque curve in the adjacent rotational speed range, as represented in fig. 5, which fig. 5 shows in particular with dashed and dotted lines by means of the initial function a_XiCorrected correction factor K_Xi. Thus, the initial function A_XiTo a certain extent, for the activation of a correction factor K in the corresponding rotational speed range_xHas an influence, among others, due to the initial function A_XiIs used in the respective adjacent rotational speed range, so that this activation of the correction factor also acts in the adjacent rotational speed range X_i。

Thus, is corrected forDrag torque curve M_{Correction of}(n) is calculated as:

M_{correction of}(n)＝M(n)·sum(K_Xi·A_Xi(n)) (2)

The corrected drag torque curve M_{Correction of}(n) is represented by a dash-dot line in the diagram of fig. 5 and is obtained by means of a predetermined drag torque curve M (n), i.e. at each speed n, the corrected drag torque curve M_{Correction of}(n) is the sum of the predetermined drag torque profile m (n) multiplied by the corrected correction factor.

Once the corrected drag torque curve has been determined in this way, in a subsequent loop iteration of the method, the rotational speed of the torque transfer section in the respective rotational speed range X can be calculated on the basis of the corrected drag torque curve, in order to be able to determine the rotational speed from the respective rotational speed deviation N while taking into account the measured rotational speed.

Once the drag torque curve has been corrected in the manner described above, this corrected drag torque curve M is taken into account when the all-wheel drive or the secondary axle is switched on later_{Correction of}(n) while the multiplate clutch 33 may be engaged so that the torque transmitting portion 36 is accelerated and increased in speed uniformly. Likewise, the clutch characteristics of the multiplate clutch 33 can be changed while taking into account the corrected drag torque curve in order to be able to smooth the switching on of the all-wheel drive as much as possible.

Claims

1. Method for correcting a drag torque curve (M (n)) of at least one rotatable mechanical element, which can be coupled in terms of drive effectively to a drive by means of a first clutch (33) and to an output of a vehicle by means of a second clutch (46), and whose drag torque depends on the rotational speed (n) of the mechanical element and therefore on the rotational speed (n) of the mechanical element, wherein the drag torque curve (M (n)) has a plurality of rotational speed ranges (X (n)) differing from one another_i)，

Wherein the drag torque curve(M (n)) in each speed range (X)_i) Based on the corresponding speed range (X) _i) Rotational speed deviation (N) of_i) At each rotation speed range (X)_i) Of said mechanical element (n)_Measuring) And a calculated speed (n) of said mechanical element_{Model (model)}) Is corrected to be in the middle of the time,

wherein in the first speed range (X)_i) Adjacent second speed range (X)_i) In separate predetermined speed ranges associated with a limited speed, the drag torque curve (M (n)) is based on a predetermined speed range (X) allocated to two adjacent speed ranges_i) Two correction factors (K)_x) Is corrected, and

wherein adjacent speed ranges (X)_i) Said correction factor (K) of_x) In the adjacent rotational speed range (X)_i) The decrease or increase in the predetermined speed band in relation to the limit speed in between is based on an initial function by: each speed range (X)_i) Is assigned an initial function (A)_Xi(n)), the initial function (A)_Xi(n)) is dependent on the rotational speed (n) and the corresponding rotational speed range (X)_i) Said correction factor (K) of_x) With the initial function (A)_Xi(n)) multiplication, wherein each initial function (A)_Xi(n)) in the initial function (A)_Xi(n)) allocated speed range (X)_i) Has the largest function value, the initial function (A)_Xi(n)) in adjacent rotational speed ranges (X) _i) Along said adjacent speed range (X) from said maximum function value_i) Continuously decreases until the function value is zero.

2. The method of claim 1,

the drag torque curve (M (n)) is generated in each speed range (X)_i) By basing it on said corresponding speed range (X)_i) Said rotational speed deviation (N) of_i) Determining the respective speed range (X) allocated to said motor vehicle_i) Correction factor (K) of_x) Corrected, the drag torque curve (M (n)) is in the corresponding speed rangeEnclose (X)_i) Based on the correction factor (K)_x) And is corrected.

3. The method according to claim 1 or 2,

said corresponding speed range (X)_i) Said rotational speed deviation (N) of_i) Is determined by counting the number of revolutions in said respective rotational speed range (X)_i) The measured rotational speed (n) of the mechanical element at different times_Measuring) With said calculated speed (n) of said mechanical element_{Model (model)}) Are determined by summing the determined rotational speed differences.

4. The method according to claim 1 or 2,

at each speed range (X)_i) The rotational speed which has been measured initially is used as the rotational speed (n) for calculation_{Model (model)}) Is started.

5. The method of claim 1,

In the predetermined speed band associated with the limit speed, the correction of the drag torque curve (M (n)) is in two adjacent speed ranges (X)_i) The following procedure was followed: in the first rotational speed range (X)_i) Is allocated to the first rotation speed range (X) as the rotation speed gradually approaches the limit rotation speed_i) Correction factor (K) of_x) Gradually reduced and allocated to a second speed range (X)_i) Correction factor (K) of_x) Gradually increase, wherein in the second rotation speed range (X)_i) Is allocated to the first rotation speed range (X) as the rotation speed becomes gradually distant from the limit rotation speed_i) Said correction factor (K) of_x) Further gradually decreases and is allocated to the second rotational speed range (X)_i) Said correction factor (K) of_x) And further gradually increases.

6. The method of claim 1,

the initial function (A)_Xi(n)) are selected such that adjacent rotational speed ranges (X)_i) Initial function (A)_Xi(n)) has a value of one at each rotational speed (n).

7. The method according to claim 1 or 2,

is assigned to a separate speed range (X) after having performed a correction of the drag torque curve (M (n)) _i) Correction factor (K) of_x) Based on the corresponding speed range (X)_i) Said rotational speed deviation (N) of_i) And updated, for this purpose, the corresponding speed range (X)_i) Said rotational speed deviation (N) of_i) By setting the speed in the corresponding speed range (X)_i) The measured rotational speed (n) of the mechanical element at different times_Measuring) A rotational speed (n) of the mechanical element calculated taking into account the corrected drag torque curve (M (n))_{Model (model)}) Are determined by summing the determined rotational speed differences.

8. The method according to claim 1 or 2,

determining the respective speed range (X) while the drag torque of the mechanical element causes a consumption of the rotational energy of the mechanical element_i) Said rotational speed deviation (N) within_i)。

9. The method of claim 1,

the mechanical element is a torque transmitting portion (36) of a vehicle driveline.

10. The method of claim 2,

the drag torque curve (M (n)) is in the corresponding speed range (X)_i) By multiplying by said correction factor (K)_x) And is corrected.

11. The method of claim 5,

is assigned to the first speed range (X) _i) Said correction factor (K) of_x) Gradually decreases until it is zero.